This invention relates to sensors of encroachment in an area. In particular, this invention relates to buried seismic sensors on land or underwater and relays arranged to detect encroachments into an area and to indicate the intrusions at remote stations.
Current methods used to stop illegal border crossings rely on the intensive use of man power. This intensive use typically takes the form of extensive patrolling of particular areas via helicopters or land vehicles. Illegal crossings are detected primarily by visual means. Clearly, this approach is unsatisfactory since the vast areas of borders that need to be patrolled and the limited number of personnel on patrol means that relatively few arrests will be made among the thousands of illegal crossings that go unchecked each year. This manpower intensive approach creates the impossible requirement that the officers on patrol need to be at numerous places at any given moment in order to detect and then apprehend the intruders. Other methods for detection use conspicuous sensors and RF broadcast towers that are so visible to violators, that they simply avoid them and cross the border where no sensors or transmitters exist. Furthermore, intruders have been known to disable transmitters and sensing stations that are visible.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for undetectable, buried seismic sensors on land or underwater using magneto-inductive signals in the ELF to VLF range to communicate intrusions to remote stations.